The present invention relates to a control apparatus for an AC motor, in particular, the present invention relates to setting of electric constants of an AC motor.
An AC motor, in particular, a permanent magnet synchronous motor has been extending the application ranges such as consumer electronics, industry, automobiles, by utilization of features of a compact size and high efficiency. In particular, in recent years, products having a motor drive system replaced from a square wave energization type to a sinusoidal wave energization type, and there has increased a controller essentially requiring input of electric constants setting values of a motor, such as resistance, inductance and back EMF (electromotive force) constant, in applications such as rotator position estimation by position sensorless control, or high precision torque control. Therefore, input without correct identification of electric constants of a motor influences on control performance very much. Among others, inductance is strongly influenced by magnetic nonlinearity of a core, and influence of magnetic saturation is expressed very much.
Technology for varying electric constants setting values of an AC motor, in response to electric current, has been shown in JP-A-2001-161099. This technology is a technology for improving torque precision by furnishing the relation between magnetic flux and electric current of a synchronous motor, as a nonlinear function, to the inside of a controller. Further, JP-A-9-327200 has shown a technology for configuring a control apparatus, in consideration of cross-magnetization effect of an armature d-axis and an armature q-axis, and magnetic field system and an armature q-axis (hereafter referred to as conventional technology 2).